Micro-electro-mechanical-system (MEMS) devices are airtightly sealed to protect the MEMS devices from external influence, similarly to general semiconductors. However, the MEMS device has a movable portion of a cantilever structure or a fixed-fixed beam structure, which is deformable by an electric force or an external force such as an acceleration force. The MEMS device has a cavity due to operating characteristics of the movable portion. Accordingly, a sealing structure capable of maintaining the state of the cavity is required to be applied thereto. A metal cap type package having been applied thereto is known as such a sealing structure. However, enlargement of the package is inevitable. Thus, recent demands for miniaturization of the MEMS device cannot be satisfied.
To cope with such a problem, a structure for sealing the MEMS device in the cavity in the following process has been proposed (see, e.g., JP-2005-123561-A). That is, a sacrificing layer for covering the MEMS device is formed. Then, a film, in which a through hole communicating with the sacrificing layer is formed, is stacked thereon. Subsequently, the sacrificing layer is selectively removed through this through hole. Then, a sealing layer is stacked thereon so as to block the through hole. Hitherto, the sealing layer has been formed by a sputtering method, a chemical vapor deposition (CVD) method or the like.
However, when the sealing layer is formed by, e.g., a CVD method, a film formation material or the like extending from the through hole is liable to adhere to the MEMS device. This degrades the characteristic of the device.